The present invention relates to wafer etching systems, and the like, and more particularly, to gas discharge apparatus comprising an annular electrode for use with wafer etching systems.
The assignee of the present invention improves the flatness of semiconductor wafers using an etching system. In order to achieve an economically practical through-put of processed wafers per hour, a sufficiently high etch rate (or volume removal rate) must be obtained. Major factors affecting the wafer etching process are the process gas flow, how it is introduced into the etching chamber, and the discharge power. The currently-used design (known as a quasi-shower head electrode) tends to require a great deal of gas flow to increase the etch rate. It exhibits erosion effects at very high power and very high gas flow rates. The quasi-shower head electrode includes several precision pieces and is relatively complex and costly to build.
The original quasi-shower head used in the etching chamber employed a two inch diameter electrode that used two gas inlet rings. This design was later changed to use three gas inlet rings. Although higher flow rates were achieved with the modified design, most of the additional flow was introduced at the periphery of the electrode and sufficiently high etch rates could not be achieved. The gas inlet rings limit the amount of gas that can be introduced into the discharge without eroding the electrode.
Therefore, it is an objective of the present invention to provide for improved gas discharge apparatus for use with wafer etching systems capable of very high etch rates comprising an annular electrode where etching gas is introduced at the center of the annulus. It is a further objective of the present invention to provide for improved gas discharge apparatus that does not exhibit the erosion effects of conventional electrodes.